Radar Level Measurement

Introduction

• Focus on radar level measurement and transmitter.
• Video covers:
  • Working principle of radar level transmitter.
  • Types of radar level transmitters.
  • Mounting guidelines.

Working Principle

• Time of Flight Measurement
  • High frequency radar pulses sent towards the tank bottom.
  • Pulses bounce off the product surface, return to the sensor.
  • Microprocessor measures time delay between sent and received pulse.
  • Calculates distance with:
    • Distance = (Speed of Light * Time Delay) / 2
• Dielectric Constant Impact
  • High dielectric products: Strong reflections, accurate measurements.
  • Low dielectric products: Absorbs pulses, less accurate.*

Types of Radar Level Instruments

1. Non-Contact Type
   • Pulse Radar Technique: Uses high frequency pulses (already explained).
   • Frequency Modulated Continuous Wave (FMCW) Radar
     • Sends microwaves of continuously varying frequency.
     • Distance proportional to frequency difference between sent and received signal.
2. Guided Wave Radar (GWR)
   • Based on Time Domain Reflectometry (TDR).
   • Pulse sent via cable/rod, reflected by medium surface.
   • Calculates fluid level from time difference of sent and reflected pulse.
   • Can measure liquid interface (e.g. oil and water).

Advantages of Guided Wave Radar

• Accurate for both liquid and solid measurement.
• Not affected by:
  • Viscosity, density, acidity changes.
  • Agitated surfaces.
  • Extreme temperature and pressure.
• Suitable for complex applications like fine powders, sticky fluids.

Non-Contact Radar Level Transmitter

• Works on time of flight or TDR principle.
• Applications: Corrosive/non-corrosive liquids, sanitary environments, small tanks.
• Advantages:
  • Accurate for liquids/solids.
  • Cost-efficient, easy to use.
  • Ideal for food, medical, chemical industries.

Comparison: Guided Wave vs Non-Contact Radar

• Frequency:
  • GWR uses high frequency radar impulses.
  • Non-contact uses microwave pulses.
• Contact:
  • GWR: Contact type.
  • Non-contact: Non-contact type.
• Performance:
  • GWR not affected by extreme conditions.
  • Non-contact affected by airspace and surface conditions.
• Mounting:
  • Both mounted on top, avoid mixers/obstacles.
• Cost:
  • GWR moderately priced.
  • Non-contact cost-effective.

Mounting Guidelines

• Install with clear, unobstructed view of product surface.
• Avoid center or above inlet stream.
  • Ideal on opposite side of inlet stream.
• Minimum distance to tank wall of 8 inches (200 mm).
• Avoid internal structures in signal beam.

Advantages of Radar Level Transmitters

• Usable with various media: liquids, sludges, slurries, some solids.
• No compensation needed for changes in density, dielectric, conductivity.
• Low maintenance due to no moving parts.
• Suitable for corrosive/dirty applications.

Limitations

• Clear view needed for accuracy.
• False echoes possible from structural elements.
• Accuracy impacted by low dielectric fluids.